Scheduling for ND takes place 5-6 years into the future without a conference affiliation. They have continually scheduled traditional powers that may or may not be good in the year they play, but historically, was an attempt to schedule a tough game (this years examples-Southern Cal, Virginia Tech, Florida St.).
They beat 10-3 Michigan, 10-3 Syracuse, 9-4 Stanford, 9-5 Northwestern, 7-6 Wake Forest, and beat bowl teams in Vandy, Pitt. The Navy rivalry is 50 years old and Ball St. was an Indiana based school scheduled as a favor (done by most SEC schools as well).
In a normal year, a schedule with Michigan, Florida St., Stanford, Va Tech, Southern Cal, & Pitt in the top 1/2 then potential landmines in Northwestern, Syracuse, Wake Forest and Vandy with Navy & Ball State as gimmes does not place ND anywhere close to having the weakest schedule of a ranked team.
This has their SOS at 14:
https://www.teamrankings.com/college-football/ranking/schedule-strength-by-other
They also only played 6 home games when nearly every team in a conference plays 7. Only 3 of their last 9 games were at home.
Neat to see SEC teams ranked 1,2,3,4,5,6,10, 11, 13 & 20.